It is frequently necessary in a number of endeavors to very accurately determine the relative position of an object and to relate the determined position to a control system or a computer so that appropriate action, based on the perceived position, can be taken. For example, with a numerically controlled machine tool, it is imperative that the working tool's position with respect to some reference location be continuously and accurately determined. Position determining transducers of various kinds are, of course, well known, and for numerical control applications, position transducers are commonly either of the encoder type or the resolver type. These devices may be responsive to either linear changes in position or to angular changes such as the angular change in a shaft's position.
The position indicative signals produced by these different types of devices are considerably different in form, however. Thus, in presenting the signals to a control system, or other instrumentation, each set of signals must be interfaced differently in order to present the signals in a form compatible to receiving instrumentation regardless of the transducer type. Conventionally, two essentially separate and distinct interfacing systems have been employed, in a sense providing two totally separate input channels into the receiving instrumentation. In the numerical control field particularly, some means has been sought by those of skill in the art whereby position sensing transducers of alternative types could be readily interfaced to the computer bus system of the controller without requiring complex, separate circuit paths and wherein an economy of circuitry is attained by using signal handling components common to the alternative transducers notwithstanding the difference in signal format.
Accordingly, it is an object of the present invention to provide apparatus for interfacing position sensing transducers of alternate types to a computer bus system, or to other instrumentation, in satisfaction of those problems and requirements outlined above. A more particular object, however, is to provide circuitry which allows either a position transducer of the encoder type or of the resolver type to be conveniently and economically interfaced to a numerical control system.